Acoustic noise suppression system, computer-implemented method therefor, computer program and non-volatile data carrier

Abstract

A transmitter unit (100) acquires a source signal (ss) representing an acoustic source signal (sA) emitted from a noise pollution source (S) and based thereon transmits a wireless signal (R[sFF]) containing a feedforward signal (sFF). A receiver unit (200) arranged at a target position (T) receives the wireless signal (R[sFF]), and based thereon feeds a cancelling signal (sc) towards a target position (T), which cancelling signal (sc) suppresses the acoustic source signal (sA) after having propagated from the noise pollution source (S) to the target position (T). A first signal processing unit (120) in the transmitter unit (100) associates time-stamp data (t1) with the feedforward signal (sFF), which time-stamp data (t1) link the source signal (ss) to a time frame (t) that is common between the first and second signal processing units (120; 220) and includes the time-stamp data (t1) in the wireless signal (R[sFF]). A second signal processing unit (220) in the receiver unit (200) produces the cancelling signal (sc) on the further basis of the time-stamp data (t1) so that the anti-noise signal (ac) is estimated to reach the target position (T) with a timing that matches a propagation time (TP) required for the acoustic source signal (sA) to travel from the noise pollution source (S) to the target position (T).

Description

TECHNICAL FIELD

[0001] The present invention relates generally to suppression of undesired sounds. Especially, the invention relates to a system according to the preamble of claim 1 and a corresponding computer-implemented method. The invention also relates to a computer program for executing the method, and a non-volatile data carrier storing such a computer program.BACKGROUND

[0002] Good sleep quality is fundamental for the health and well-being of all humans. Disturbing noise is an important reason for poor sleep quality. In our modern life, snoring constitutes one example of such a disturbance. This is especially true for individuals who share sleeping environment with a snorer.

[0003] US 2014 / 0276227 describes an apparatus and method that can provide for snore detection and management in the form of either wearable devices or non-wearable devices, or a combination thereof. In some examples, a method includes receiving an acoustic signal, characterizing the acoustic signal as a snoring sound to determine presence of a snoring condition, and transmitting a notification signal to cause notification of the detection of the snoring sound. Optionally, the method can include receiving the notification signal and causing a notification source to notify of the presence of a snoring condition or any other sleep disturbance. For example, the notification source can be configured to impart vibrations unto a source of the snoring sound, responsive to the vibratory activation signal, to indicate the presence of the snoring condition.

[0004] WO 2016 / 124252 discloses a method for generating a first sound filter for suppression of snoring induced sounds comprises recording a first sound signal at a first measurement location in proximity of a source of snoring sounds, recording a second sound signal at a second measurement location in proximity of a person to be isolated from snoring sounds, determining a first snoring sound signal from the source by comparing the first sound signal with the second sound signal and setting first adaptive filters based on the first snoring sound signal. The disclosure further relates to systems for generating sound filters, and methods and systems for suppressing snoring induced sounds.

[0005] US 10,242,657 reveals a kit for attenuation of noise. The kit includes a noise source audio transducer, two earpieces, and a control unit. The two earpieces have respective resilient bodies that engage outer portions of ear canals of respective ears of a user while respective in-ear transducers of the two earpieces are respectively positioned in inner portions of the ear canals. The respective in-ear transducers detect discrepancies (e.g., incomplete superpositio-ning) between the noise and the anti-noise. The respective in-ear transducers optionally detect respective secondary path effects in the ear canals. The noise source audio transducer detects noise generated by a noise source (e.g., snoring noise). The control unit configures an adaptive filter based at least in part on an error signal, and optionally based in part on secondary path effects. The control unit generates signals representative of anti-noise. The two earpieces produce the anti-noise responsive to the signals. The two earpieces produce masking noise with sound level that varies in direct correlation with sound level of the noise generated by the noise source.

[0006] Thus, various solutions are known for tackling undesired sounds in a sleeping environment. However, none of the known solutions is capable of reducing, for example snoring-related sounds so efficiently that a subject located right next to the noise source can rest assured that he / she will not be disturbed by the emanating noise.SUMMARY

[0007] The object of the present invention is therefore to offer an improved solution for acoustic noise suppression that addresses the above problem.

[0008] According to one aspect of the invention, the object is achieved by an acoustic noise suppression system that includes a transmitter unit adapted to be arranged at a noise pollution source, for example near or on a snorer, and a receiver unit adapted to be arranged at a target position, for example in the ear channel of a user. The transmitter unit, in turn, contains a first microphone, a first signal processing unit and a first wireless interface. The first microphone is configured to acquire a source signal that represents an acoustic source signal emitted from the noise pollution source. The first signal processing unit is configured to produce a feedforward signal, e.g. of a digital format based on the source signal. The feedforward signal thus describes an audible stream of soundwaves comprised in the acoustic source signal. The first wireless interface is configured to transmit a wireless signal, e.g. a radio signal that contains the feedforward signal. The receiver unit, in turn, contains a second wireless interface, a second signal processing unit and an audio sound transducer, for instance in the form of a speaker. The second wireless interface is configured to receive the wireless signal. The second signal processing unit is configured to produce a cancelling signal based on the wireless signal, which cancelling signal is adapted to form a basis for an anti-noise signal suppressing the acoustic source signal after having propagated through a fluid, typically air, from the noise pollution source to the target position. The audio sound transducer is configured to generate the anti-noise signal based on the cancelling signal and feed the anti-noise signal towards the target position. In particular, the first signal processing unit is configured to associate time-stamp data with the feedforward signal, which time-stamp data link the source signal to a time frame that is common between the first and second signal processing units. The first signal processing unit is also configured to include the time-stamp data in the wireless signal. Moreover, the second signal processing unit is configured to produce the cancelling signal on the further basis of the time-stamp data so that the anti-noise signal is estimated to reach the target position with a timing that matches a propagation time required for the acoustic source signal to travel through the fluid from the noise pollution source to the target position.

[0009] This system is advantageous because it enables preemptive cancellation at the target position of the stream of soundwaves that emanate from the acoustic noise source. Namely, due to the difference in propagation speeds between the acoustic noise signal and the wireless signal it is possible for the feedforward signal to reach the receiver unit sufficiently in advance of the acoustic noise signal to allow the receiver unit to produce a truly cancelling anti-noise signal at the target position.

[0010] Of course, this may be useful also for avoiding undesired sounds from any kind of known sources, for instance household appliances or machinery in the home.

[0011] According to one embodiment of this aspect of the invention, the second signal processing unit is configured to produce the cancelling signal so that the anti-noise signal contains a stream of soundwaves with such amplitude variations that the anti-noise signal is estimated to cancel out the audible stream of soundwaves comprised in the acoustic source signal at the target position. In other words, the streams of soundwaves in the acoustic source signal and the anti-noise signal respectively combine in a destructive manner at the target position, such that they cancel one another in this point. As a result, the acoustic source signal becomes inaudible at the target position.

[0012] According to another embodiment of this aspect of the invention, the receiver unit is communicatively connected to a second microphone that is configured to acquire a target signal representing the acoustic source signal after having propagated through the fluid from the noise pollution source to the target position. The receiver unit further contains a digital memory configured to store a representation of the target signal. The second signal processing unit is here also configured to: derive a reference signal from the wireless signal, correlate the stored representation of the target signal with the reference signal to, based thereon, and with reference to the common time frame determine the propagation time. Namely, by comparing a first time stamp designating when the acoustic source signal was acquired by the transmitter unit with a second time stamp designating when the acoustic source signal reached the receiver unit, the second signal processing unit may determine the propagation time between the noise pollution source and the target position. Hence, it is possible to adjust the timing, or phase offset, for the anti-noise signal appropriately.

[0013] Preferably, each of the reference signal and the target signal contains a respective series of sample values, e.g. of a digital format, and the second signal processing unit is configured to correlate the stored representation of the target signal with the reference signal as follows. A first set of consecutive sample values from the series of sample values in the reference signal in a first temporal window are compared with a second set of consecutive sample values from the series of sample values in the target signal in a second temporal window, where the first temporal window covers an extension in time that is equal to an extension in time covered by the second temporal window. The propagation time is determined as a time shift between the first and second temporal windows with respect to the common time frame as expressed by the time stamp data. Here, the propagation time is determined as a time shift at which the first and second sets of consecutive sample values fulfil a similarity criterion, typically equivalent to a positive correlation peak.

[0014] According to one embodiment of this aspect of the invention, the second signal processing unit is configured to determine the propagation time at least during a setup procedure for the system, such that an appropriate timing, or phase offset, for the anti-noise signal may be set correctly.

[0015] It is further be preferable if the second signal processing unit is configured to repeat the determining of the propagation time at repeated occasions during operation of the system, such that timing, or phase offset, for the anti-noise signal may recalibrated, for example to compensate for any relative movements between the transmitter and receiver units.

[0016] Specifically, according to one embodiment of the invention, the transmitter unit contains a first clock generator that is configured to generate a first basis for the time frame in relation to which first basis the first signal processing unit is configured to associate time-stamp data to the feedforward signal. Analogously, the receiver unit contains a second clock generator that is configured to generate a second basis for the time frame in relation to which second basis the second signal processing unit is configured to produce the cancelling signal. The first and second clock generators are synchronized to one another. Thereby, it can be ensured that the timing, or phase offset, for the anti-noise signal may be set appropriately to cancel out the acoustic source signal at the target position.

[0017] To maintain the synchronization between the first and second clock generators each of the first and second clock generators may further be communicatively connected to a clock source, e.g. a GNSS (Global Navigation Satellite System), a mobile communication system or a radio beacon that provides a common clock signal to the first and second clock generators. The first clock generator is further configured to generate the first basis for the time frame based on the common clock signal and the second clock generator is further configured to generate the second basis for the time frame based on the common clock signal.

[0018] According to yet another embodiment of this aspect of the invention, the transmitter unit is adapted to be arranged at the noise pollution source in the form of a potential snorer and the receiver unit is adapted to be arranged at the target position in the form of a user wishing to avoid being disturbed by the potential snorer, typically a person sharing a sleeping environment with the snorer. Thereby, the sleep of the latter is liberated from snoring interference.

[0019] According to another embodiment of this aspect of the invention, the first microphone is disposed on a chinstrap, a headband and / or an adhesive tape adapted to be worn by a subject. Thereby, a source signal in the form of snoring may be acquired in an efficient manner.

[0020] According to still another embodiment of this aspect of the invention, the system further includes a server that is communicatively connected both to a network and a database. Here, each of the transmitter and receiver units also contains a respective first and second network interface that is configured to be communicatively connected to the network. Moreover, the first signal processing unit is configured to process the source signal to derive acoustic source data that characterize the source signal in terms of: occurrence, duration, repetitive pattern behavior, waveforms and / or frequency spectra; and cause the first network interface to send the acoustic source data via the network to the server. The server is configured to: store the acoustic source data in the database; analyze the acoustic source data that have been stored in the database over a period to derive at least one typical feature of the source signal; and based on the at least one typical feature generate at least one supporting parameter; and send the at least one supporting parameter via the network to the receiver unit. The receiver unit is configured to obtain the at least one supporting parameter through the second network interface; and produce the cancelling signal on the further basis of the at least one supporting parameter. Consequently, the overall efficiency of the system can be improved. Namely, based on conclusions made from earlier experiences, the server may guide the receiver unit to suppress the source signal from the snorer in a highly efficient manner even though only a relatively small amount of data is fed via the wireless signal from the transmitter unit.

[0021] Additionally, the receiver unit may be comprised in an earphone unit adapted to be worn by a subject, for instance an in-ear earpiece or a headphone. This namely enables an efficient forwarding of the anti-noise signal to a target position in the form of a user's organ of hearing.

[0022] According to yet another embodiment of this aspect of the invention, the first signal processing unit is configured to monitor a signal strength of the source signal acquired via the first microphone, and if the signal strength subceeds a first threshold level, control the first wireless interface to a standby mode in which the first wireless interface does not transmit the wireless signal. If, during a period when the first wireless interface is in the standby mode, the signal strength exceeds a second threshold level above the first threshold level, the first signal processing unit is configured to control the first wireless interface to an active mode in which the first wireless interface transmits the wireless signal. Consequently, the first wireless interface may be controlled to only operate when needed. Thus, power may be conserved, and the battery life is prolonged.

[0023] Alternatively, or in addition, according to another embodiment of this aspect of the invention, the second signal processing unit is configured to monitor the second wireless interface, and if the wireless signal is not received via the second wireless interface, the second signal processing unit is configured to control the audio sound transducer to generate the anti-noise signal such that the anti-noise signal contains a stream of a default masking soundwaves. Namely, the absence of the wireless signal may be due to the fact that the first microphone has been dislocated, or the transmitter unit does not operate as intended, and in such a case, the default masking soundwaves may mitigate the disturbing sound.

[0024] According to still another embodiment of this aspect of the invention, the first and wireless interfaces are configured to communicate data according to at least one of the standards BLE (Bluetooth Low Energy), Bluetooth, ANT (Adaptive Network Topology), UWB (Ultra Wide Band), Zigbee (IEEE 802.15.4) and Wireless USB (Universal Serial Bus), which all provide efficient means for short-distance radio transmissions.

[0025] According to another aspect of the invention, the object is achieved by a computer-implemented method for acoustic noise suppression, which method involves the steps of: acquiring, via a first microphone, a source signal that represents an acoustic source signal emitted from a noise pollution source; producing, in a first signal processing unit, a feedforward signal, which feedforward signal is based on the source signal and describes an audible stream of soundwaves comprised in the acoustic source signal; transmitting, via a first wireless interface, a wireless signal that comprises the feedforward signal; receiving, via a second wireless interface, the wireless signal; producing, in a second signal processing unit, a cancelling signal, which cancelling signal is based on the wireless signal and is adapted to form a basis for an anti-noise signal suppressing the acoustic source signal after having propagated through a fluid from the noise pollution source to the target position; generating, via an audio sound transducer, the anti-noise signal, which anti-noise signal is based on the cancelling signal and is fed towards the target position. associating, in the first signal processing unit, time-stamp data with the feedforward signal, which time-stamp data link the source signal to a time frame being common between the first and second signal processing units; including the time-stamp data in the wireless signal; and producing, in the second signal processing unit, the cancelling signal on the further basis of the time-stamp data, so that the anti-noise signal is estimated to reach the target position with a timing that matches a propagation time required for the acoustic source signal to travel through the fluid from the noise pollution source to the target position.

[0026] The advantages of this method are apparent from the discussion above with reference to the proposed system.

[0027] According to a further aspect of the invention, the object is achieved by a computer program loadable into a non-volatile data carrier communicatively connected to at least one processing unit. The computer program includes software for executing the above method when the program is run on the at least processing unit.

[0028] According to another aspect of the invention, the object is achieved by a non-volatile data carrier containing the above computer program.

[0029] Further advantages, beneficial features and applications of the present invention will be apparent from the following description and the dependent claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The invention is now to be explained more closely by means of preferred embodiments, which are disclosed as examples, and with reference to the attached drawings. Figure 1shows a block diagram of an acoustic noise suppression system according to a first embodiment of the invention; Figures 2a-cshow examples that illustrate how various signals may be generated according to one embodiment of the invention; Figures 3 - 5exemplify how a transmitter unit may be arranged according to embodiments of the invention; Figure 6illustrates how a receiver unit may be arranged according to one embodiment of the invention; Figure 7illustrates how a wireless interface and a processing unit may be implemented according to one embodiment of the invention; Figure 8shows a block diagram of an acoustic noise suppression system according to a second embodiment of the invention; and Figure 9illustrates, by means of a flow diagram, the general method for acoustic noise suppression according to the invention. DETAILED DESCRIPTION

[0031] Figure 1 shows a block diagram of a block diagram of an acoustic noise suppression system according to a first embodiment of the invention. The system includes a transmitter unit 100 and a receiver unit 200.

[0032] The transmitter unit 100 is adapted to be arranged at a noise pollution source S, which for example may be represented by a person who is inclined to snore. Nevertheless, according to the invention, the noise pollution source S may be constituted by arbitrary transmitter of undesired soundwaves, such as a household appliance or a piece of machinery. The transmitter unit 100, in turn, includes a first microphone 110, a first signal processing unit 120 and a first wireless interface 130.

[0033] The first microphone 110 is configured to acquire a source signal ss that represents an acoustic source signal s A that is emitted from the noise pollution source S. In other words, the first microphone is transducer, which is arranged to convert mechanical energy in the form of sound waves into audio signals in the form of electrical energy.

[0034] The first signal processing unit 120 is configured to produce a feedforward signal s FF based on the source signal ss. Here, the feedforward signal s FF describes, for example in the form of digital samples, an audible stream of soundwaves that are comprised in the acoustic source signal s A . The feedforward signal s FF thus has a format that is suitable for transmission over a wireless channel, which, for example may be implemented by radio or optical technology.

[0035] According to embodiments of the invention, the first and wireless interfaces 130 and 230 are configured to communicate data according to at least one of the standards BLE, Bluetooth, ANT, UWB, Zigbee and Wireless USB.

[0036] Referring now to Figures 2a - 2c, which show examples illustrating how various signals may be generated according to one embodiment of the invention. The first signal processing unit 120 is also configured to associate time-stamp data t 1 with the feedforward signal s FF . The time-stamp data t 1 link the source signal ss to a time frame t that is common between the first and second signal processing units 120 and 220 respectively.

[0037] The first signal processing unit 120 may include a microcontroller with integrated Digital Signal Processing (DSP) capabilities, for example from STM32L4 series by STMicroelectronics that is configured to processes the source signal ss into the feedforward signal SFF.

[0038] The first wireless interface 130 is configured to transmit a wireless signal R[s FF ] that carries the feedforward signal s FF . The wireless signal R[s FF ] further contains the time-stamp data t 1 , so that each piece of information in the wireless signal R[s FF ] is related to the common time frame t. The first wireless interface 130 may include radio transmitter circuitry and / or an optical transmitter.

[0039] The receiver unit 200 is adapted to be arranged at a target position T, which typically is represented by a person who does not want to be disturbed by the source signal ss emanating from the noise pollution source S. Consequently, the target position T may be represented by a user's organ of hearing.

[0040] The receiver unit 200, in turn, contains a second wireless interface 230, a second signal processing unit 220 and an audio sound transducer 210.

[0041] The second wireless interface 230 is configured to receive the wireless signal R[s FF ] on a format that matches the format used by the first wireless interface 130. I.e. the second wireless interface 230 may include radio receiver circuitry and / or an optical receiver.

[0042] The second signal processing unit 220 is configured to produce a cancelling signal sc based on the wireless signal R[s FF ], which cancelling signal sc is adapted to form a basis for an anti-noise signal ac suppressing the acoustic source signal s A after having propagated through a fluid, typically air, from the noise pollution source S to the target position T. Analogous to the first signal processing unit 120, the second signal processing unit 220 may include a microcontroller with integrated DSP capabilities, for example from STM32L4 series by STMicroelectronics that is configured to processes the wireless signal R[s FF ] into cancelling signal sc as will be described below. Specifically, the second signal processing unit 220 is configured to produce the cancelling signal sc on the further basis of the time-stamp data t 1 , so that the anti-noise signal ac is estimated to reach the target position T with a timing that matches a propagation time T P required for the acoustic source signal s A to travel through the fluid from the noise pollution source S to the target position T. Assuming that the distance between the noise pollution source S to the target position T is approximately 50 cm and the fluid is air at normal air pressure, the propagation time T P becomes around 1.5 ms. Figure 2b illustrates the acoustic source signal s A at the arrival at the target position T at a point in time t 2 in relation to the common time frame t. Provided that the wireless signal R[s FF ] travels at the speed of light from the transmitter unit 100 to the receiver unit 200, the corresponding propagation time for the wireless signal R[s FF ] is negligible. This means that the second signal processing unit 220 has 1.0 to 1.5 seconds at its disposal to generate the anti-noise signal ac. Since, as will be discussed below, the signal processing is fairly straightforward, this places a moderate processing demand on the second signal processing unit 220.

[0043] The audio sound transducer 210, in turn, is configured to generate the anti-noise signal ac based on the cancelling signal sc, and feed the anti-noise signal ac towards the target position T. Thus, the audio sound transducer 210 may be represented by a speaker, for example included in an earpiece or a headphone.

[0044] According to one embodiment of the invention, the second signal processing unit 220 is configured to produce the cancelling signal sc so that the anti-noise signal ac contains a stream of soundwaves with such amplitude variations that the anti-noise signal ac is estimated to cancel out the audible stream of soundwaves comprised in the acoustic source signal s A at the target position T. In short, this means that the anti-noise signal ac shall be generated such that at a point in time when the acoustic source signal s A is estimated to have a particular amplitude at the target position T, the cancelling signal sc should have the same amplitude, however of opposite sign at the target position T. Figure 2c schematically illustrates this in relation to a target signal s T that represents the acoustic source signal s A . As a result of this destructive combination of the acoustic source signal s A at and the anti-noise signal ac the acoustic source signal s A becomes inaudible at the target position T.

[0045] To facilitate determining the propagation time T P between the noise pollution source S and the target position T, according to one embodiment of the invention, the receiver unit 200 is communicatively connected to a second microphone 215, which preferably is arranged as close as possible to the target position T. The second microphone 215 is configured to acquire the target signal s T that represents the acoustic source signal s A after having propagated through the fluid, say air, from the noise pollution source S to the target position T. The receiver unit 200 further contains a digital memory 240 that is configured to store a representation of the target signal s T , which has been registered by the second microphone 215 during a measurement interval. Additionally, the second signal processing unit 220 is configured to derive a reference signal s AR from the wireless signal R[s FF ], for example through demodulation, and correlate the stored representation of the target signal s T with the reference signal s AR . Based on the correlation and with reference to said common time frame t, the second signal processing unit 220 is configured to determine the propagation time T P .

[0046] For example, each of the reference signal s AR and the target signal s T may be represented by a respective series of sample values, and the second signal processing unit 220 may be configured to correlate the stored representation of the target signal s T with the reference signal s AR by comparing a first set of consecutive sample values from the series of sample values in the reference signal s AR in a first temporal window W1 with a second set of consecutive sample values from the series of sample values in the target signal s T in a second temporal window W2, where the first temporal window W1 covers an extension in time that is equal to an extension in time covered by the second temporal window W2. In other words, the first and second temporal windows W1 and W2 contain equally many sample values. The second signal processing unit 220 is then configured to determine the propagation time T P as a time shift, respect to said common time frame t, between the first and second temporal windows W1 and W2 at which time shift the first and second sets of consecutive sample values fulfil a similarity criterion.

[0047] Preferably, the second signal processing unit 220 is configured to determine the propagation time T P at least during a setup procedure for the system. In a use case where the noise pollution source S is snorer and the target position T is a neighboring person's ear channel, the distance between the source S and the target position T typically remains essentially constant.

[0048] However, to maintain good cancellation of the source signal ss over time, it is generally preferable that the second signal processing unit 220 is configured to repeat the determining of the propagation time T P at repeated occasions during operation of the system, say once per minute, once every ten minutes, or once per hour.

[0049] According to one embodiment of the invention, to ensure that the common the time frame t remains stable and reliable, the transmitter unit 100 contains a first clock generator 145 and the receiver unit 200 contains a second clock generator 245. The first clock generator 145 is configured to generate a first basis for the time frame t in relation to which first basis the first signal processing unit 120 is configured to associate time-stamp data t 1 to the feedforward signal s FF . The second clock generator 245 is configured to generate a second basis for the time frame t in relation to which second basis the second signal processing unit 220 is configured to produce the cancelling signal sc. The first and second clock generators 145 and 245 are mutually synchronized to one another, preferably via an external resource.

[0050] According to one embodiment of the invention, each of the first and second clock generators 145 and 245 is communicatively connected to a clock source 150 that provides a common clock signal CLK to the first and second clock generators 145 and 245 respectively. Here, the first clock generator 145 is configured to generate the first basis for the time frame t based on the common clock signal CLK and the second clock generator 245 is configured to generate the second basis for the time frame t based on the common clock signal CLK. The clock source 150 may be a resource of a GNSS, a mobile communication system and / or a radio beacon to which the acoustic noise suppression system is connected.

[0051] Figures 3 to 5 exemplify how a transmitter unit 100 may be arranged according to embodiments of the invention.

[0052] As mentioned above, the transmitter unit 100 is preferably adapted to be arranged at the noise pollution source S in the form of a subject 300 being a potential snorer. To this aim, the first microphone 110 may be disposed on a chinstrap 310 carried by the subject 300 as illustrated. Alternatively, the first microphone 110 may be disposed on a headband 410 worn by the subject 300, for example together with the entire transmitter unit 100 as illustrated in Figure 4. As yet another alternative, the first microphone 110 may be disposed on an adhesive tape 510 attached to subject 300, for example on his / her cheek as illustrated in Figure 5.

[0053] The receiver unit 200 is preferably adapted to be arranged at the target position T in the form of a user who wishes to avoid being disturbed by the subject 300.

[0054] Figure 6 illustrates how the receiver unit 200 is arranged in a user's ear 600 according to one embodiment of the invention. Here, the receiver unit 200, in turn, is included in an earphone unit 610, which is adapted to be worn by the user in his / her external ear canal. This design is advantageous because it enables an efficient cancellation of the source signal ss and makes it possible to arrange the second microphone 215 at a suitable position near the user's ear canal.

[0055] To conserve energy and thus allow a relatively long battery life of a power source of the transmitter unit 100, the first signal processing unit 120 is preferably adapted to switch its operation between an active mode and a standby mode. The power source may be a rechargeable LiPo battery, e.g., Panasonic CG-320 with a capacity of 20 mAh.

[0056] According to one embodiment of the invention, the first signal processing unit 120 is configured to monitor a signal strength of the source signal ss acquired via the first microphone 110. If the signal strength subceeds a first threshold level, the first signal processing unit 120 is configured to control the first wireless interface 130 to the standby mode in which the first wireless interface 130 does not transmit the wireless signal R[s FF ]. If, during a period when the first wireless interface 130 is in the standby mode, the signal strength exceeds a second threshold level above the first threshold level, the first signal processing unit 120 is configured to control the first wireless interface 130 to an active mode in which the first wireless interface 130 transmits the wireless signal R[s FF ].

[0057] Although the above is generally advantageous because such an altering between also reduces the energy consumption of the receiver unit 200, there may be situations where the receiver unit 200 may operate autonomously, i.e. without input from the transmitter unit 100. For example, the absence of the wireless signal R[s FF ] may also be due to the fact that the first microphone 115 has been dislocated from the noise pollution source S, or the transmitter unit 100 does not operate as intended. In such a case, a default masking soundwaves may mitigate the disturbing sound emanating from the noise pollution source S.

[0058] Therefore, according to one embodiment of the invention, the second signal processing unit 220 is configured to monitor the second wireless interface 230. If the wireless signal R[s FF ] is not received via the second wireless interface 230 during a predefined interval, say 10 to 60 minutes, the second signal processing unit 220 is configured to control the audio sound transducer 210 to generate the anti-noise signal ac, such that the anti-noise signal ac comprises a stream of a default masking soundwaves, for example white noise.

[0059] Figure 7 illustrates a block diagram of the second processing unit 220 in the receiver unit 200 according to one embodiment of the invention. It is generally advantageous if the second processing unit 220 is configured to effect the above procedure in an automatic manner by executing a computer program 725 in a processor device 710, which is communicatively connected to a memory unit 720, i.e. non-volatile data carrier, storing a computer program 725, which, in turn, contains software for making the processor 710 execute the actions mentioned in this disclosure when the computer program 725 is run on the processor 710.

[0060] Figure 8 shows a block diagram of an acoustic noise suppression system according to a second embodiment of the invention. In Figure 8, all entities and signals that also occur in any of Figures 1 to 7 designate the entities and signals described above with reference to these Figures.

[0061] The system shown in Figure 8 includes a server 830 that is communicatively connected to a network 830, e.g. the Internet. Hence, the network 830, in turn, may be comprised of two or more wired and / or wireless networks that are connected to one another. Further, the server 830 is communicatively connected to a database 835, either directly, or via one or more networks, such as the network 830.

[0062] The transmitter unit 100 here also includes a first network interface 810 that is configured to be communicatively connected to the network 800, for instance via an intermediate Wi-Fi and / or cellular / mobile network. Analogously, the receiver unit 200 includes a second network interface 820, which likewise is configured to be communicatively connected to the network 800. As a result, both the transmitter unit 100 and the receiver unit 200 may exchange data with the server 830.

[0063] Additionally, the first signal processing unit 120 is configured to process the source signal ss to derive acoustic source data D AS therefrom, which acoustic source data D AS characterize the source signal ss in terms of occurrence of the acoustic source signal s A being emitted from the noise pollution source S, the duration of the acoustic source signal s A , any repetitive pattern behavior of the acoustic source signal s A , the waveforms represented by the acoustic source signal s A and / or the frequency spectra, of the acoustic source signal s A . The first signal processing unit 120 is also configured to cause the first network interface 810 to send the acoustic source data D AS via the network 800 to the server 830.

[0064] The server 830 is configured to store the acoustic source data D AS in the database 835, preferably in an anonymized / integrity washed format, and when a predefined amount of the acoustic source data D AS has been stored and / or a predefined period has elapsed, analyze the acoustic source data D AS stored in the database 835 to derive at least one typical feature of the source signal ss. Based on the at least one typical feature, in turn, the server 830 is configured to generate at least one supporting parameter Ps, which is adapted to aid the receiver unit 200 to produce cancelling signal sc at high quality, however based on a relatively small amount of data being carried by the wireless signal R[s FF ] from the transmitter unit 100.

[0065] The server 830 is configured to send the at least one supporting parameter Ps via the network 800 to the receiver unit 200.

[0066] The receiver unit 200 is further configured to obtain the at least one supporting parameter Ps through the second network interface 820 and produce the cancelling signal sc on the further basis of the at least one supporting parameter Ps, either at an enhanced quality relative to if the cancelling signal sc had been produced exclusively based on the on the wireless signal R[s FF ], or based on less data from the transmitter unit 100 than what was needed in the embodiment described above with reference to Figure 1.

[0067] Preferably, a software for interacting with the server 830, the transmitter unit 100 and / or the receiver unit 200 is provided, which software is downloadable to and installable in a user terminal, e.g. a smartphone. Thereby, via the software, a user may control the operation of the transmitter unit 100, the receiver unit 200 and / or the interaction with the server 830 in a straightforward manner.

[0068] To sum up, and with reference to the flow diagram in Figure 9, we will now describe the computer-implemented method according to the invention for acoustic noise suppression, which method is controlled by the first and second signal processors 120 and 220 respectively.

[0069] In a first step 910, a source signal ss is acquired via a first microphone 110. The source signal ss represents an acoustic source signal s A emitted from a noise pollution source S.

[0070] A subsequent step 920 produces a feedforward signal s FF in a first signal processing unit 120. The feedforward signal s FF is based on the source signal ss and describes an audible stream of soundwaves comprised in the acoustic source signal s A . The first signal processing unit 120 associates time-stamp data with the feedforward signal s FF , which time-stamp data link the source signal ss to a time frame that is common between the first and second signal processing units 120 and 220. The first signal processing unit 120 also includes the time-stamp data in the wireless signal R[s FF ].

[0071] In a following step 930, a wireless signal R[s FF ] is transmitted via a first wireless interface 130, which wireless signal R[s FF ] comprises the feedforward signal s FF . In a step 940, a second wireless interface 230 receives the wireless signal (R[s FF ]); Thereafter, in a step 950, the second signal processing unit 220 produces a cancelling signal sc, which is based on the wireless signal R[s FF ] and is adapted to form a basis for an anti-noise signal ac that suppresses the acoustic source signal s A after having propagated through a fluid from the noise pollution source S to the target position T. The second signal processing unit 220 produces the cancelling signal sc on the further basis of the time-stamp data, so that the anti-noise signal ac is estimated to reach the target position T with a timing, or offset, that matches a propagation time T P required for the acoustic source signal s A to travel through the fluid from the noise pollution source S to the target position T.

[0072] Then, in a step 960, an audio sound transducer 210 generates the anti-noise signal ac, which is based on the cancelling signal sc and is fed towards the target position T.

[0073] The process steps described with reference to Figure 9 may be controlled by means of a programmed processor. Moreover, although the embodiments of the invention described above with reference to the drawings comprise processor and processes performed in at least one processor, the invention thus also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the invention into practice. The program may be in the form of source code, object code, a code intermediate source and object code such as in partially compiled form, or in any other form suitable for use in the implementation of the process according to the invention. The program may either be a part of an operating system or be a separate application. The carrier may be any entity or device capable of carrying the program. For example, the carrier may comprise a storage medium, such as a Flash memory, a ROM (Read Only Memory), for example a DVD (Digital Video / Versatile Disk), a CD (Compact Disc) or a semiconductor ROM, an EPROM (Erasable Programmable Read-Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), or a magnetic recording medium, for example a floppy disc or hard disc. Further, the carrier may be a transmissible carrier such as an electrical or optical signal which may be conveyed via electrical or optical cable or by radio or by other means. When the program is embodied in a signal, which may be conveyed, directly by a cable or other device or means, the carrier may be constituted by such cable or device or means. Alternatively, the carrier may be an integrated circuit in which the program is embedded, the integrated circuit being adapted for performing, or for use in the performance of, the relevant processes.

[0074] Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0075] The term "comprises / comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components. The term does not preclude the presence or addition of one or more additional elements, features, integers, steps or components or groups thereof. The indefinite article "a" or "an" does not exclude a plurality. In the claims, the word "or" is not to be interpreted as an exclusive or (sometimes referred to as "XOR"). On the contrary, expressions such as "A or B" covers all the cases "A and not B", "B and not A" and "A and B", unless otherwise indicated. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

[0076] It is also to be noted that features from the various embodiments described herein may freely be combined, unless it is explicitly stated that such a combination would be unsuitable.

[0077] The invention is not restricted to the described embodiments in the figures, however, may be varied freely within the scope of the claims. Any subject-matter falling outside the scope of the claims is provided for information purposes, only.

Claims

1. An acoustic noise suppression system, comprising: a transmitter unit (100) adapted to be arranged at a noise pollution source (S), which transmitter unit (100) comprises: a first microphone (110) configured to acquire a source signal (ss) that represents an acoustic source signal (sA) emitted from the noise pollution source (S), a first signal processing unit (120) configured to produce a feedforward signal (sFF) based on the source signal (ss), which feedforward signal (sFF) describes an audible stream of soundwaves comprised in the acoustic source signal (sa), a first wireless interface (130) configured to transmit a wireless signal (R[sFF]) comprising the feedforward signal (SFF), a receiver unit (200) adapted to be arranged at a target position (T), which receiver unit (200) comprises: a second wireless interface (230) configured to receive the wireless signal (R[sFF]), a second signal processing unit (220) configured to produce a cancelling signal (sc) based on the wireless signal (R[sFF]), which cancelling signal (sc) is adapted to form a basis for an anti-noise signal (ac) suppressing the acoustic source signal (sA) after having propagated through a fluid from the noise pollution source (S) to the target position (T), and an audio sound transducer (210) configured to generate the anti-noise signal (ac) based on the cancelling signal (sc), which anti-noise signal (ac) is fed towards the target position (T), characterized in that the first signal processing unit (120) is further configured to associate time-stamp data (t1) with the feedforward signal (sFF), which time-stamp data (t1) link the source signal (ss) to a time frame (t) being common between the first and second signal processing units (120; 220), and which time-stamp data (t1) are comprised in the wireless signal (R[sFF]), and the second signal processing unit (220) is configured to produce the cancelling signal (sc) on the further basis of the time-stamp data (t1) so that the anti-noise signal (ac) is estimated to reach the target position (T) with a timing that matches a propagation time (TP) required for the acoustic source signal (sA) to travel through the fluid from the noise pollution source (S) to the target position (T).

2. The system according to claim 1, wherein the second signal processing unit (220) is configured to produce the cancelling signal (sc) so that the anti-noise signal (ac) comprises a stream of soundwaves with such amplitude variations that the anti-noise signal (ac) is estimated to cancel out the audible stream of soundwaves comprised in the acoustic source signal (sA) at the target position (T).

3. The system according to claim 2, wherein: the receiver unit (200) is communicatively connected to a second microphone (215) configured to acquire a target signal (sT) that represents the acoustic source signal (sA) after having propagated through the fluid from the noise pollution source (S) to the target position (T), the receiver unit (200) further comprises a digital memory (240) configured to store a representation of the target signal (sT), and the second signal processing unit (220) is further configured to: derive a reference signal (sAR) from the wireless signal (R[sFF]), correlate the stored representation of the target signal (sT) with the reference signal (sAR) to based thereon and with reference to said common time frame (t), determine the propagation time (TP).

4. The system according to claim 3, wherein each of the reference signal (sAR) and the target signal (sT) comprises a respective series of sample values, and the second signal processing unit (220) is configured to correlate the stored representation of the target signal (sT) with the reference signal (sAR) by: comparing a first set of consecutive sample values from the series of sample values in the reference signal (sAR) in a first temporal window (W1) with a second set of consecutive sample values from the series of sample values in the target signal (sT) in a second temporal window (W2), which first temporal window (W1) covers an extension in time that is equal to an extension in time covered by the second temporal window (W2), and determining the propagation time (TP) as a time shift between the first and second temporal windows (W1; W2) with respect to said common time frame (t) at which time shift the first and second sets of consecutive sample values fulfil a similarity criterion.

5. The system according to any of claims 3 or 4, wherein the second signal processing unit (220) is configured to determine the propagation time (TP) during a setup procedure for the system.

6. The system according to any one of claims 3 to 5, wherein the second signal processing unit (220) is configured to repeat the determining of the propagation time (TP) at repeated occasions during operation of the system.

7. The system according to any one of the preceding claims, wherein: the transmitter unit (100) comprises a first clock generator (145) configured to generate a first basis for the time frame (t) in relation to which first basis the first signal processing unit (120) is configured to associate time-stamp data (t1) to the feedforward signal (sFF), the receiver unit (200) comprises a second clock generator (245) configured to generate a second basis for the time frame (t) in relation to which second basis the second signal processing unit (220) is configured to produce the cancelling signal (sc), and the first and second clock generators (145; 245) are synchronized to one another.

8. The system according to claim 7, wherein each of the first and second clock generators (145; 245) is communicatively connected to a clock source (150) that provides a common clock signal (CLK) to the first and second clock generators (145; 245), wherein the first clock generator (145) is configured to generate the first basis for the time frame (t) based on the common clock signal (CLK) and the second clock generator (245) is configured to generate the second basis for the time frame (t) based on the common clock signal (CLK).

9. The system according to any one of the preceding claims, wherein the transmitter unit (100) is adapted to be arranged at the noise pollution source (S) in the form of a potential snorer and the receiver unit (200) is adapted to be arranged at the target position (T) in the form of a user wishing to avoid being disturbed by the potential snorer.

10. The system according to any one of the preceding claims, wherein the first microphone (110) is disposed on at least one of: a chinstrap (310), a headband (410) and an adhesive tape (510) adapted to be worn by a subject (300).

11. The system according to any one of claims 9 or 10, further comprising a server (830) communicatively connected to a network (830), which server (830) is further communicatively connected to a database (835), wherein the transmitter unit (100) comprises a first network interface (810) configured to be communicatively connected to the network (800) and the receiver unit (200) comprises a second network interface (820) configured to be communicatively connected to the network (800), wherein the first signal processing unit (120) is configured to: process the source signal (ss) to derive acoustic source data (DAS) that characterize the source signal (ss) in terms of at least one of: occurrence, duration, repetitive pattern behavior, waveforms and frequency spectra, and cause the first network interface (810) to send the acoustic source data (DAS) via the network (800) to the server (830), wherein the server (830) is configured to: store the acoustic source data (DAS) in the database (835), analyze the acoustic source data (DAS) that have been stored in the database (835) over a period to derive at least one typical feature of the source signal (ss), and based on the at least one typical feature generate at least one supporting parameter (Ps), and send the at least one supporting parameter (Ps) via the network (800) to the receiver unit (200), and wherein the receiver unit (200) is configured to: obtain the at least one supporting parameter (Ps) through the second network interface (820), and produce the cancelling signal (sc) on the further basis of the at least one supporting parameter (Ps).

12. The system according to any one of the preceding claims, wherein the receiver unit (200) is comprised in an earphone unit (610) adapted to be worn by a subject.

13. The system according to any one of the preceding claims, wherein the first signal processing unit (120) is configured to: monitor a signal strength of the source signal (ss) acquired via the first microphone (110), and if the signal strength subceeds a first threshold level, control the first wireless interface (130) to a standby mode in which the first wireless interface (130) does not transmit the wireless signal (R[sFF]), and if, during a period when the first wireless interface (130) is in the standby mode, the signal strength exceeds a second threshold level above the first threshold level, control the first wireless interface (130) to an active mode in which the first wireless interface (130) transmits the wireless signal (R[sFF]).

14. The system according to any one of the preceding claims, wherein the second signal processing unit (220) is configured to: monitor the second wireless interface (230), and if the wireless signal (R[sFF]) is not received via the second wireless interface (230), control the audio sound transducer (210) to generate the anti-noise signal (ac) such that the anti-noise signal (ac) comprises a stream of a default masking soundwaves.

15. The system according to any one of the preceding claims, wherein the first and wireless interfaces (130, 230) are configured to communicate data according to at least one of the standards BLE, Bluetooth, ANT, UWB, Zigbee and Wireless USB.

16. A computer-implemented method for acoustic noise suppression, which method comprises: acquiring, via a first microphone (110), a source signal (ss) that represents an acoustic source signal (sA) emitted from a noise pollution source (S); producing, in a first signal processing unit (120), a feedforward signal (sFF), which feedforward signal (sFF) is based on the source signal (ss) and describes an audible stream of soundwaves comprised in the acoustic source signal (sa); transmitting, via a first wireless interface (130), a wireless signal (R[sFF]) that comprises the feedforward signal (sFF); receiving, via a second wireless interface (230), the wireless signal (R[sFF]); producing, in a second signal processing unit (220), a cancelling signal (sc), which cancelling signal (sc) is based on the wireless signal (R[sFF]) and is adapted to form a basis for an anti-noise signal (ac) suppressing the acoustic source signal (sA) after having propagated through a fluid from the noise pollution source (S) to the target position (T); and generating, via an audio sound transducer (210), the anti-noise signal (ac), which anti-noise signal (ac) is based on the cancelling signal (sc) and is fed towards the target position (T), characterized by the method further comprising: associating, in the first signal processing unit (120), time-stamp data (t1) with the feedforward signal (sFF), which time-stamp data (t1) link the source signal (ss) to a time frame (t) being common between the first and second signal processing units (120; 220); including the time-stamp data (t1) in the wireless signal (R[sFF]), and producing, in the second signal processing unit (220), the cancelling signal (sc) on the further basis of the time-stamp data (t1) so that the anti-noise signal (ac) is estimated to reach the target position (T) with a timing that matches a propagation time (TP) required for the acoustic source signal (sA) to travel through the fluid from the noise pollution source (S) to the target position (T).

17. A computer program (725) loadable into a non-volatile data carrier (720) communicatively connected to a processor (710), the computer program (725) comprising software for executing the method according to claim 16 when the computer program (725) is run on the processor (710).

18. A non-volatile data carrier (720) containing the computer program (725) of claim 17.

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